Look closely at that curve in the waist, the arc of the hand: do these models look unnatural, not to mention surprisingly similar? It's only once you see them lined up that it becomes clear – they are computer-generated mannequins with the heads and skin colour of real models added. Which makes dummies of us all for not realising sooner.

Yesterday's response from H&M, the world's second biggest retailer, was particularly ironic given that youth groups and schools are today to give evidence to the all party parliamentary group on body confidence on why girls and women, and increasingly boys and men, are so distressed about the way they look. Several studies, including one on media influences on girls between nine and 12 by Marika Tiggemann and Levina Clark, indicated that nearly half want to be thinner, and as a result have engaged in a diet or are aware of the concept of dieting. Sexist imagery in advertising is nothing new: witness this season's Harvey Nichols ad. In 2003, Teen magazine reported that 35 per cent of girls 6 to 12 years old have been on at least one diet, and that 50 to 70 per cent of normal weight girls believe they are overweight

Natasha Walter, author of the aptly named Living Dolls: The Return of Sexism, says: "What's so extraordinary about the H&M models is that everybody would just accept it. That says something about how normal it has become to use artificial images of women. We just brush past them. The worrying thing is it gets into your head, particularly the heads of young women."

One way forward is for the Advertising Standards Authority to insist on a disclaimer in the same way it did with mascara companies pretending that fake eyelashes were down to the stroke of a brush. A spokesman for the ASA says all advertising has a "social responsibility" to resist any possible "mental, moral and physical harm", especially on young minds. However, it can only act on complaints and so far it has received none.

Susie Orbach, psychotherapist and writer, sees a silver lining of sorts: "Perhaps this will expose the constructed nature of the images more graphically than all the critiques of Photoshopping. Perhaps it will be easier to say: this body does not exist, it is a fiction." We live in hope.